11. 1-B 2-A 3-B 12. We must use cars instead of cars and buses; We mustn't drop litter in the streets; We must recycle paper, cans and glass; We must provide more litter bins; We mustn't build factories around our city/town; We must plant more trees and flowers; We mustn't build more parks; We mustn't pour chemicals into the water; We mustn't pollute the air
